Interface circuit for high speed communication, and system including the same

ABSTRACT

A system may include an interface circuit and a plurality of wire buses electrically coupled with one another. The interface circuit may include transmitters which change states of the plurality of wire buses to transmit a plurality of multilevel symbols. The transmitters may drive wire buses, coupled to each other, to a termination voltage level.

CROSS-REFERENCES TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. §119(a) toKorean application number 10-2015-0099090, filed on Jul. 13, 2015, inthe Korean Intellectual Property Office, which is incorporated herein byreference in its entirety.

BACKGROUND

1. Technical Field

Various embodiments generally relate to a communication system, and moreparticularly, to an interface circuit for high speed communication and asystem including the same.

2. Related Art

Electronic products for personal uses, such as a personal computer, atablet PC, a laptop computer and a smart phone, may be configured byvarious electronic components. Two different electronic components inthe electronic products may communicate at a high speed to process alarge amount of data within a short time. The electronic components maygenerally communicate through interface circuits. The electroniccomponents may communicate in various schemes. For example, theelectronic components may communicate with a serial communicationscheme.

As the performances of electronic components are improved, necessity fora communication scheme capable of increasing bandwidth and reducingpower consumption has increased. In order to meet such necessities,various new serial communication schemes are suggested in the art, andimproved interface circuits for supporting the new serial communicationschemes are being developed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a representation of an example of theconfiguration of a system in accordance with an embodiment.

FIG. 2 is a diagram illustrating a representation of an example of theconfiguration of a memory system in accordance with an embodiment.

FIG. 3 is a diagram illustrating a representation of an example of theconfiguration of a system in accordance with an embodiment.

FIG. 4 is a diagram illustrating a representation of an example of theconfiguration of the system illustrated in FIG. 3.

DETAILED DESCRIPTION

In an embodiment, an interface circuit may be provided The interfacecircuit may include a transmitter coupled with a plurality of wirebuses, and may be configured to change states of the plurality of wirebuses to transmit a plurality of multilevel symbols. The adjacent wirebuses may be electrically coupled with each other, and the transmittermay drive the adjacent wire buses to a termination voltage level.

In an embodiment, a system may be provided. The system may include afirst wire bus transmitter configured to change a state of a first wirebus based on a first multilevel symbol. The system may include a secondwire bus transmitter configured to change a state of a second wire busbased on a second multilevel symbol. As the first wire bus transmitterpull-up drives at least one wire of the first wire bus and the secondwire bus transmitter pull-down drives at least one wire of the secondwire bus, the first and second wire buses may be driven to a terminationvoltage level.

In an embodiment, a system may be provided. The system may include afirst wire bus transmitter configured to drive states of first to thirdwires to a high or low level based on a first multilevel symbol. Thesystem may include a second wire bus transmitter configured to drivestates of fourth to sixth wires to a high or low level based on a secondmultilevel symbol. As the first wire bus transmitter drives one of thefirst to third wires to a high level and the second wire bus transmitterdrives one of the fourth to sixth wires to a low level, the first tosixth wires may be driven to a middle level.

In an embodiment, a system may be provided. The system may include afirst wire bus transmitter configured to change a state of a first wirebus based on a first multilevel symbol, and a second wire bustransmitter configured to change a state of a second wire bus based on asecond multilevel symbol. The first wire bus may include a first wirehaving one end coupled to a first output driver and an other end coupledto a first common node, and a second wire having one end coupled to asecond output driver and an other end coupled to the first common node.The second wire bus may include a third wire having one end coupled to athird output driver and an other end coupled to a second common node,and a fourth wire having one end coupled to a fourth output driver andan other end coupled to the second common node. Each of the first,second, third, and fourth drivers include, respectively, a pull-updriver and a pull-down driver configured to drive the first second thirdand fourth wires, respectively, to a high or low level.

In an embodiment, an interface circuit may be provided. The interfacecircuit may include a transmitter coupled with a plurality of wirebuses, and configured to change states of the plurality of wire buses totransmit a plurality of multilevel symbols. Wire buses may beelectrically coupled with each other, and the transmitter may drive thewire buses, coupled with each other, to a termination voltage level.

Hereinafter, an interface circuit for high speed communication and asystem including the same will be described below with reference to theaccompanying drawings through various examples of embodiments.

Referring to FIG. 1, a system 1 in accordance with an embodiment mayinclude a master device 110 and a slave device 120. The master device110 may be a host device which controls the slave device 120. The masterdevice 110 may perform a calculation operation, and may generate variouscontrol signals for controlling the slave device 120. The slave device120 may perform various operations by being controlled by the masterdevice 110. The master device 110 and the slave device 120 may configureone link. The master device 110 and the slave device 120 may communicatethrough sub links. For example, the master device 110 and the slavedevice 120 may include interface circuits, respectively, to communicateat a high speed. The master device 110 and the slave device 120 may becoupled through signal transmission lines, and may exchange signalsthrough the signal transmission lines and the interface circuits.

The system 1 in accordance with the embodiment may communicate in abalanced code multilevel signal transmission scheme. The master device110 and the slave device 120 may be coupled through a wire bus. The wirebus may include a plurality of wire groups, and each wire group mayinclude a plurality of wires. For example, the wire bus may be a 3-wirebus, and each wire group may include 3 wires. The 3 wires of each wiregroup may be driven to voltage levels corresponding to a symbol to betransmitted from the master device 110 to the slave device 120 or fromthe slave device 120 to the master device 110. The 3 wires of each wiregroup may be driven to a high level, a middle level and a low level totransmit the symbol. For example, the high level may be a voltage levelcorresponding to ¾ V, the middle level may be a voltage levelcorresponding to ½ V, and the low level may be a voltage levelcorresponding to ¼ V. For example, the high level may be a voltage levelthat is higher than a middle level and a low level, the middle level maybe a voltage level that is less than a high level and greater than a lowlevel, and a low level may be a voltage level that is lower than a highlevel and a middle level.

Referring to FIG. 1, the master device 110 may include an encoding block111 and a transmitter 112. The encoding block 111 and the transmitter112 may be an interface circuit for balanced code multilevel signaltransmission. The encoding block 111 may encode data D<0:n> (i.e., n maybe a number) into a plurality of multilevel symbols. The encoding block111 may be a 16:7 mapper which converts 16-bit data into 7 multilevelsymbols. The transmitter 112 may receive the plurality of multilevelsymbols outputted from the encoding block 111. The transmitter 112 maychange the voltage levels or states of the 3-wire bus according to themultilevel symbols. The multilevel symbols may be, for example, 3-levelsymbols, and each symbol may include 3 phases. The 3-level symbols mayinclude first to sixth symbols. The first to sixth symbols may bedefined as +x, −x, +y, −y, +z and −z. The first symbol +x may have thephases of 1, 0, 0, the second symbol −x may have the phases of 0, 1, 1,the third symbol +y may have the phases of 0, 1, 0, the fourth symbol −ymay have the phases of 1, 0, 1, the fifth symbol +z may have the phasesof 0, 0, 1, and the sixth symbol −z may have the phases of 1, 1, 0.Since the transmitter 112 should change the voltage levels or states ofthe 3-wire bus according to the multilevel symbols, the transmitter 112may not use a symbol which has the phases of 0, 0, 0 or 1, 1, 1.

In order to transmit the first symbol +x, the transmitter 112 may changethe states of 3 wires A, B and C to the high level of ¾ V, the low levelof ¼ V and the middle level of ½ V, respectively. In order to transmitthe second symbol −x, the transmitter 112 may change the states of 3wires A, B and C to the low level of ¼ V, the high level of ¾ V and themiddle level of ½ V, respectively. In order to transmit the third symbol+y, the transmitter 112 may change the states of 3 wires A, B and C tothe middle level of ½ V, the high level of ¾ V and the low level of ¼ V,respectively. In order to transmit the fourth symbol −y, the transmitter112 may change the states of 3 wires A, B and C to the middle level of ½V, the low level of ¼ V and the high level of ¾ V, respectively. Inorder to transmit the fifth symbol +z, the transmitter 112 may changethe states of 3 wires A, B and C to the low level of ¼ V, the middlelevel of ½ V and the high level of ¾ V, respectively. In order totransmit the sixth symbol −z, the transmitter 112 may change the statesof 3 wires A, B and C to the high level of ¾ V, the middle level of ½ Vand the low level of ¼ V, respectively.

The slave device 120 may include a receiver 121 and a decoding block122. The receiver 121 and the decoding block 122 may be an interfacecircuit for balanced code multilevel signal reception. The receiver 121may be coupled with the 3-wire bus, and may receive the plurality ofmultilevel symbols according to the voltage levels of the 3-wire bus.While not illustrated, the receiver 121 may include 3 differentialbuffers in correspondence to 3 wires. The 3 differential buffers may becoupled with at least 2 of the 3 wires A, B and C. For example, a firstdifferential buffer may output the first phase of a multilevel symbol bydifferentially amplifying the voltage level difference A−B of the firstwire and the second wire, a second differential buffer may output thesecond phase of the multilevel symbol by differentially amplifying thevoltage level difference B−C of the second wire and the third wire, anda third differential buffer may generate the third phase of themultilevel symbol by differentially amplifying the voltage leveldifference C−A of the third wire and the first wire. Therefore, thereceiver 121 may output the same multilevel symbols as the multilevelsymbols transmitted through the transmitter 112, according to the statesor voltage levels of the 3-wire bus.

For example, in the case where the first symbol +x is transmitted, thevoltage level of the first wire A may be ¾ V, the voltage level of thesecond wire B may be ¼ V, and the voltage level of the third wire C maybe ½ V. The receiver 121 may output the first phase of the multilevelsymbol as 1 by differentially amplifying the voltage level differenceA−B of +½ V of the first and second wires, may output the second phaseof the multilevel symbol as 0 by differentially amplifying the voltagelevel difference B−C of −¼ V of the second and third wires, and mayoutput the third phase of the multilevel symbol as 0 by differentiallyamplifying the voltage level difference C−A of -¼ V of the third andfirst wires.

The decoding block 122 may decode multilevel symbols into data. Thedecoding block 122 may be a 7:16 demapper which decodes 7 multilevelsymbols into 16-bit data. The encoding scheme of the encoding block 111and the decoding scheme of the decoding block 122 may be complementaryto each other. While FIG. 1 illustrates an example in which data aretransmitted from the master device 110 to the slave device 120, it is tobe noted that the embodiment is not limited to such an example. Theslave device 120 may further include components such as the encodingblock 111 and the transmitter 112 to transmit data to the master device110, and the master device 110 may further include components such asthe receiver 121 and the decoding block 122 to receive data from theslave device 120.

Referring to FIG. 1, the master device 110 may control the operation ofthe slave device 120. The master device 110 may execute an operationsystem and perform various calculation functions in an electronicdevice. For example, the master device 110 may include a processor, andthe processor may include a central processing unit (CPU), a graphicprocessing unit (GPU), a multimedia processor (MMP) or a digital signalprocessor (DSP). Also, the master device 110 may be realized in the formof a system-on-chip (SoC) by combining processor chips having variousfunctions, such as application processors.

The slave device 120 may perform various operations by being controlledby the master device 110. The slave device 120 may include allcomponents which operate by being controlled by the master device 110.For example, the slave device 120 may include a system memory, a powercontroller, or a module such as a communication module, a multimediamodule and an input/output module capable of performing variousfunctions. For example, the slave device 120 may be a memory device. Thememory device may include a volatile memory device such as an SRAM(static RAM), a DRAM (dynamic RAM) and an SDRAM (synchronous DRAM) ormay include at least one of nonvolatile memory devices such as a ROM(read only memory), a PROM (programmable ROM), an EEPROM (electricallyerasable and programmable ROM), an EPROM (electrically programmableROM), a flash memory, a PRAM (phase change RAM), an MRAM (magnetic RAM),an RRAM (resistive RAM) and an FRAM (ferroelectric RAM).

FIG. 2 is a diagram illustrating a representation of an example of theconfiguration of a memory system in accordance with an embodiment.Referring to FIG. 2, a memory system 2 in accordance with an embodimentmay include a memory controller 210 and a memory device 220. The memorycontroller 210 and the memory device 220 may communicate with each otherthrough a plurality of buses. The memory controller 210 may be a masterdevice, and the memory device 220 may be a slave device which iscontrolled in its operation by the memory controller 210. The memorycontroller 210 may communicate with an external host device, and mayprovide various control signals for controlling the memory device 220,to the memory device 220. The memory controller 210 and the memorydevice 220 may communicate with each other in a balanced code multilevelsignal transmission scheme. The memory controller 210 and the memorydevice 220 may transmit multilevel symbols in series. The multilevelsymbols may be signals which are generated by encoding general binarydata and control signals to have a plurality of levels, states orphases. For example, the multilevel symbols may be 3-level symbols.

The plurality of buses may include first to third buses 231, 232 and233. The first bus 231 may be a command bus. The first bus 231 as asignal transmission line group for transmitting a command and an addresssignal CA may transmit multilevel symbols in which the command and theaddress signal CA, a clock enable signal CKE and a chip select signal CSare encoded. The second bus 232 may be a clock bus. The second bus 232may be a signal transmission line group which transmits a clock CLK. Thethird bus 233 may be a data bus. The third bus 233 may be a signaltransmission line group which transmits multilevel symbols in which aplurality of data DQ are encoded. The plurality of symbols which aretransmitted through the third bus 233 may include not only informationon the data DQ but also information on a data strobe signal DQS and/or adata masking signal DM. The plurality of symbols which are transmittedthrough the third bus 233 may be signals in which all the information onthe data DQ, the data strobe signal DQS and the data masking signal DMis encoded.

The memory controller 210 and the memory device 220 may perform a writeoperation and a read operation. In the write and read operations, thememory controller 210 may provide to the memory device 220 the pluralityof symbols which have the information on the command and address signalCA, through the first bus 231, and the clock CLK through the second bus232. In the write operation, the memory controller 210 may provide thesymbols which have the information on the data DQ and the data strobesignal DQS, to the memory device 220 through the third bus 233. In anembodiment, the memory controller 210 may include the information on thedata masking signal DM in the symbols. In the read operation, the memorydevice 220 may provide the symbols which have the information on thedata DQ and the data strobe signal DQS, to the memory controller 210through the third bus 233.

Each memory controller 210 and memory device 220 may include atransmission interface circuit which generates symbols to be transmittedthrough the third bus 233 and a reception interface circuit whichrecovers the symbols into original data and data strobe signal. Forexample, the transmission interface circuit may correspond to theencoding block 111 and the transmitter 112 illustrated in FIG. 1, andthe reception interface circuit may correspond to the receiver 121 andthe decoding block 122 illustrated in FIG. 1.

FIG. 3 is a diagram illustrating a representation of an example of theconfiguration of a system 3 in accordance with an embodiment. Referringto FIG. 3, the system 3 may include an interface circuit of atransmission device and an interface circuit of a reception device. Theinterface circuit of the transmission device and the interface circuitof the reception device may be coupled through a plurality of wirebuses. The interface circuit of the transmission device may include atransmitter 310. The transmitter 310 may be coupled with the pluralityof wire buses, and may change states of the plurality of wire busesbased on a plurality of multilevel symbols to transmit the plurality ofmultilevel symbols to the interface circuit of the reception device. Theinterface circuit of the reception device may include a receiver 320.The receiver 320 may be coupled with the plurality of wire buses, andmay receive the plurality of multilevel symbols based on states of theplurality of wire buses.

Adjacent 2 wire buses among the plurality of wire buses may beelectrically coupled with each other. The transmitter 310 may driveadjacent 2 wire buses to a termination voltage level. When themultilevel symbols are 3-level symbols and each wire bus includes 3wires to transmit a 3-level symbol, the 3 wires may have states of ahigh level, a middle level and a low level, respectively. The high levelmay be, for example but not limited to, a level corresponding to ¾ V,the middle level may be a level corresponding to ½ V, and the low levelmay be a level corresponding to ¼ V. The termination voltage level maybe a level corresponding to the middle level.

The plurality of wire buses may include first to third wire buses 301,302 and 303. While the embodiment illustrated is an example in which thesystem 3 includes 3 wire buses, it is to be noted that the embodimentsare not limited to such an example. For example, more or less than theamount of wire buses may be used than illustrated and more or less thanthe amount of wires may be used than illustrated. The second wire bus302 may be adjacent to the first wire bus 301, and the third wire bus303 may be adjacent to the second wire bus 302. In an embodiment,adjacent wire buses may be electrically coupled with each other. Forexample, the first wire bus 301 and the second wire bus 302 may becoupled with each other, and the third wire bus 303 may not be coupledwith the first and second wire buses 301 and 302. In an embodiment, thesecond wire bus 302 and the third wire bus 303 may be coupled with eachother, and the first wire bus 301 may not be coupled with the second andthird wire buses 302 and 303. Of course, while the first wire bus 301and the third wire bus 303 may be coupled with each other, since thefirst and third wire buses 301 and 303 are not adjacent to each other,inefficiency is likely to occur in comparison with the above 2 examples.

When the first and second wire buses 301 and 302 are coupled, thetransmitter 310 may drive at lease one wire of the first wire bus 301and drive at least one wire of the second wire bus 302, and, thereby,drive the first and second wire buses 301 and 302 to the terminationvoltage level. The transmitter 310 may pull-up drive at lest one wire ofthe first wire bus 301, and pull-down drive at lest one wire of thesecond wire bus 302. Accordingly, the wires of the first and second wirebuses 301 and 302 may be driven to the middle level. Conversely, thetransmitter 310 may pull-down drive at lest one wire of the first wirebus 301, and pull-up drive at lest one wire of the second wire bus 302.In other words, in order to drive adjacent 2 wire buses to thetermination voltage level, the transmitter 310 may pull-up or pull-downdrive at least one wire of one wire bus and pull-down or pull-up driveat least one wire of the other wire bus adjacent to the one wire bus. Inorder to drive the third wire bus 303 to the termination voltage level,the transmitter 310 may drive at lest one wire of the third wire bus 303to the middle level. Namely, the transmitter 310 may simultaneouslypull-up and pull-down drive at least one wire of the third wire bus 303.

When the second and third wire buses 302 and 303 are coupled, thetransmitter 310 may drive at lease one wire of the second wire bus 302and drive at least one wire of the third wire bus 303, and, thereby,drive the second and third wire buses 302 and 303 to the terminationvoltage level. The transmitter 310 may pull-up drive at lest one wire ofthe second wire bus 302, and pull-down drive at lest one wire of thethird wire bus 303. In order to drive the first wire bus 301 to thetermination voltage level, the transmitter 310 may drive at lest onewire of the first wire bus 301 to the middle level.

Each of the first to third wire buses 301, 302 and 303 may include aplurality of wires. The number of wires may be changed in correspondenceto a multilevel symbol. When the transmitter 310 transmits 3-levelsymbols, each of the first to third wire buses 301, 302 and 303 mayinclude 3 wires. For example, the first wire bus 301 may include firstto third wires A1, B1 and C1, the second wire bus 302 may include fourthto sixth wires A2, B2 and C2, and the third wire bus 303 may includeseventh to ninth wires A3, B3 and C3.

Referring to FIG. 3, the transmitter 310 may include first to third wirebus transmitters 311, 312 and 313. The first wire bus transmitter 311may be coupled with the first wire bus 301, and change a state of thefirst wire bus 301 based on a first multilevel symbol. The second wirebus transmitter 312 may be coupled with the second wire bus 302, andchange a state of the second wire bus 302 based on a second multilevelsymbol. The third wire bus transmitter 313 may be coupled with the thirdwire bus 303, and change a state of the third wire bus 303 based on athird multilevel symbol. The first to third wire bus transmitters 311,312 and 313 may change states of the first to third wire buses 301, 302and 303 to transmit the first to third multilevel symbols, respectively.When the first and second wire buses 301 and 302 are coupled, the firstwire bus transmitter 311 may drive 2 wires among the first to thirdwires A1, B1 and C1 to a high or low level according to the firstmultilevel symbol, and drive the remaining 1 wire among the first tothird wires A1, B1 and C1 to a high level. The second wire bustransmitter 312 may drive 2 wires among the fourth to sixth wires A2, B2and C2 to a high or low level according to the second multilevel symbol,and drive the remaining 1 wire among the fourth to sixth wires A2, B2and C2 to a low level. Similarly, when the second and third wire buses302 and 303 are coupled, the second wire bus transmitter 312 may drive 2wires among the fourth to sixth wires A2, B2 and C2 to a high or lowlevel according to the second multilevel symbol, and drive the remaining1 wire among the fourth to sixth wires A2, B2 and C2 to a high level.The third wire bus transmitter 313 may drive 2 wires among the seventhto ninth wires A3, B3 and C3 to a high or low level according to thethird multilevel symbol, and drive the remaining 1 wire among theseventh to ninth wires A3, B3 and C3 to a low level.

The receiver 320 may include first to third wire bus receivers 321, 322and 323. The first wire bus receiver 321 may be coupled with the firstwire bus 301, and receive the first multilevel symbol transmitted fromthe first wire bus transmitter 311. The first wire bus receiver 321 maygenerate a multilevel symbol based on a state of the first wire bus 301,and the multilevel symbol may correspond to the first multilevel symbol.The second wire bus receiver 322 may be coupled with the second wire bus302, and receive the second multilevel symbol transmitted from thesecond wire bus transmitter 312. The second wire bus receiver 322 maygenerate a multilevel symbol based on a state of the second wire bus302, and the multilevel symbol may correspond to the second multilevelsymbol. The third wire bus receiver 323 may be coupled with the thirdwire bus 303, and receive the third multilevel symbol transmitted fromthe third wire bus transmitter 313. The third wire bus receiver 323 maygenerate a multilevel symbol based on a state of the third wire bus 303,and the multilevel symbol may correspond to the third multilevel symbol.

The system 3 may further include a termination circuit 330. Thetermination circuit 330 may include a plurality of termination resistorsRT. The termination circuit 330 may include termination resistors RThaving one ends which are respectively coupled with the first to thirdwires A1, B1 and C1 and the other ends which are coupled with a firstcommon node NA. The termination circuit 330 may include terminationresistors RT having one ends which are respectively coupled with thefourth to sixth wires A2, B2 and C2 and the other ends which are coupledwith a second common node NB. The termination circuit 330 may includetermination resistors RT having one ends which are respectively coupledwith the seventh to ninth wires A3, B3 and C3 and the other ends whichare coupled with a third common node NC.

FIG. 4 is a diagram illustrating a representation of an example of theconfiguration of the system 3 illustrated in FIG. 3. Referring to FIG.4, the first wire bus transmitter 311 may include first to third outputdrivers 411, 412 and 413, the second wire bus transmitter 312 mayinclude fourth to sixth output drivers 421, 422 and 423, and the thirdwire bus transmitter 313 may include seventh to ninth output drivers431, 432 and 433. The first to ninth output drivers 411, 412, 413, 421,422, 423, 431, 432 and 433 may be coupled with the first to ninth wiresA1, B1, C1, A2, B2, C2, A3, B3 and C3, respectively, and include pull-updrivers and pull-down drivers which pull-up and pull-down drive thefirst to ninth wires A1, B1, C1, A2, B2, C2, A3, B3 and C3. The first tothird output drivers 411, 412 and 413 may pull-up or pull-down drive thefirst to third wires A1, B1 and C1, respectively, in response to pull-upsignals PUA1, PUB1 and PUC1 and pull-down signals PDA1, PDB1 and PDC1which are generated based on the first multilevel symbol. The fourth tosixth output drivers 421, 422 and 423 may pull-up or pull-down drive thefourth to sixth wires A2, B2 and C2, respectively, in response topull-up signals PUA2, PUB2 and PUC2 and pull-down signals PDA2, PDB2 andPDC2 which are generated based on the second multilevel symbol. Theseventh to ninth output drivers 431, 432 and 433 may pull-up orpull-down drive the seventh to ninth wires A3, B3 and C3, respectively,in response to pull-up signals PUA3, PUB3 and PUC3 and pull-down signalsPDA3, PDB3 and PDC3 which are generated based on the third multilevelsymbol. While not illustrated, the system 3 may further include acontroller or control circuit for providing pull-up and pull-downsignals to the first to ninth output drivers 411, 412, 413, 421, 422,423, 431, 432 and 433 based on the first to third multilevel symbols.

The first wire bus receiver 321 may include first to third receptiondrivers 441, 442 and 443. The first reception driver 441 may be coupledwith the first and second wires A1 and B1. The first reception driver441 may differentially amplify states of the first and second wires A1and B1. The second reception driver 442 may be coupled with the secondand third wires B1 and C1. The second reception driver 442 maydifferentially amplify states of the second and third wires B1 and C1.The third reception driver 443 may be coupled with the third and firstwires C1 and A1. The third reception driver 443 may differentiallyamplify states of the third and first wires C1 and A1. Outputs of thefirst to third reception drivers 441, 442 and 443 may be a multilevelsymbol.

The second wire bus receiver 322 may include fourth to sixth receptiondrivers 451, 452 and 453. The fourth reception driver 451 may be coupledwith the fourth and fifth wires A2 and B2. The fourth reception driver451 may differentially amplify states of the fourth and fifth wires A2and B2. The fifth reception driver 452 may be coupled with the fifth andsixth wires B2 and C2. The fifth reception driver 452 may differentiallyamplify states of the fifth and sixth wires B2 and C2. The sixthreception driver 453 may be coupled with the sixth and fourth wires C2and A2. The sixth reception driver 453 may differentially amplify statesof the sixth and fourth wires C2 and A2. Outputs of the fourth to sixthreception drivers 451, 452 and 453 may be a multilevel symbol.

The third wire bus receiver 323 may include seventh to ninth receptiondrivers 461, 462 and 463. The seventh reception driver 461 may becoupled with the seventh and eighth wires A3 and B3. The seventhreception driver 461 may differentially amplify states of the seventhand eighth wires A3 and B3. The eighth reception driver 462 may becoupled with the eighth and ninth wires B3 and C3. The eighth receptiondriver 462 may differentially amplify states of the eighth and ninthwires B3 and C3. The ninth reception driver 463 may be coupled with theninth and seventh wires C3 and A3. The ninth reception driver 463 maydifferentially amplify states of the ninth and seventh wires C3 and A3.Outputs of the seventh to ninth reception drivers 461, 462 and 463 maybe a multilevel symbol.

Reception termination resistors RRT may be coupled between the first tothird wires A1, B1 and C1 and the first common node NA. Receptiontermination resistors RRT may be coupled between the fourth to sixthwires A2, B2 and C2 and the second common node NB. Reception terminationresistors RRT may be coupled between the seventh to ninth wires A3, B3and C3 and the third common node NC. The resistance value of thereception termination resistors RRT may be R (i.e., R may be a number).Transmission termination resistors RTT may be coupled between thepull-up and pull-down drivers of the first output driver 411 and thefirst wire A1. Similarly, transmission termination resistors RTT may berespectively coupled between the pull-up and pull-down drivers of thesecond to ninth output drivers 412, 413, 421, 422, 423, 431, 432 and 433and the second to ninth wires B1, C1, A2, B2, C2, A3, B3 and C3. Theresistance value of the transmission termination resistors RTT may be R(i.e., R may be a number). However, the resistance value of certaintransmission termination resistors RTT may be 2R.

In the system 3, adjacent wire buses may be coupled with each other. Forexample, the first to third wires A1, B1 and C1 may be coupled with thefourth to sixth wires A2, B2 and C2. The seventh to ninth wires A3, B3and C3 may not be coupled with the first to sixth wires A1, B1, C1, A2,B2 and C2. The first to third output drivers 411, 412 and 413 may changethe states of the first to third wires A1, B1 and C1 based on the firstmultilevel symbol, and the fourth to sixth output drivers 421, 422 and423 may change the states of the fourth to sixth wires A2, B2 and C2based on the second multilevel symbol. For example, it is assumed thatthe first multilevel symbol is the first symbol +x and the secondmultilevel symbol is the second symbol −x. In this example, as may bereadily seen from FIG. 1, the first output driver 411 may drive thefirst wire A1 to the high level, the second output driver 412 may drivethe second wire B1 to the low level, and the third output driver 413 maydrive the third wire C1 to the middle level. The fourth output driver421 may drive the fourth wire A2 to the low level, the fifth outputdriver 422 may drive the fifth wire B2 to the high level, and the sixthoutput driver 423 may drive the sixth wire C2 to the middle level. Inthe system 3 in accordance with an embodiment, the first output driver411 may pull-up drive the first wire A1 according to the pull-up signalPUA1, and the second output driver 412 may pull-down drive the secondwire B1 according to the pull-down signal PDB1. Further, the fourthoutput driver 421 may pull-down drive the fourth wire A2 according tothe pull-down signal PDA2, and the fifth output driver 422 may pull-updrive the fifth wire B2 according to the pull-up signal PUB2. The thirdoutput driver 413 may drive the third wire C1 to the high level, and thesixth output driver 423 may drive the sixth wire C2 to the low level.That is to say, the third wire C1 may be pull-up driven as the pull-updriver of the third output driver 413 is turned on according to thepull-up signal PUC1, and the sixth wire C2 may be pull-down driven asthe pull-down driver of the sixth output driver 423 is turned onaccording to the pull-down signal PDC2. Since the third and sixth wiresC1 and C2 are coupled with each other, the third and sixth wires C1 andC2 may be driven together to the middle level. The pull-down driver ofthe third output driver 413 and the pull-up driver of the sixth outputdriver 423 may be turned off. In the conventional art, in order to drivethe third wire C1 to the middle level, both the pull-up and pull-downdrivers of the third output driver 413 are turned on and simultaneouslypull-up and pull-down drive the third wire C1. Similarly, in order todrive the sixth wire C2 to the middle level, both the pull-up andpull-down drivers of the sixth output driver 423 are turned on andsimultaneously pull-up and pull-down drive the sixth wire C2. Incontrast with this, in an embodiment, since only the pull-up driver ofthe third output driver 413 is turned on and only the pull-down driverof the sixth output driver 423 is turned on to drive the third and sixthwires C1 and C2 to the middle level, power consumption for driving thethird and sixth wires C1 and C2 to the middle level may be reduced.

In an embodiment, the resistance value of transmission terminationresistors RTT coupled between the pull-up and pull-down drivers of anoutput driver for driving a wire to the middle level and the wire may be2R. The resistance value of the transmission termination resistors RTTmay be changed according to a multilevel symbol. The transmissiontermination resistors RTT may be configured by variable resistors. Theresistance value of transmission termination resistors RTT coupled withan output driver for driving a wire to the high or low level accordingto a multilevel symbol may be controlled to R, and the resistance valueof transmission termination resistors RTT coupled with an output driverfor driving a wire to the middle level may be controlled to 2R. In theexample where the first and second wire bus transmitters 311 and 312transmit the first and second symbols +x and −x, respectively, asdescribed above, the resistance value of the transmission terminationresistors RTT coupled with the first output driver, the second outputdriver, the fourth output driver and the fifth output driver may becontrolled to be R. The resistance value of the transmission terminationresistors RTT coupled with the third output driver and the sixth outputdriver may be controlled to be 2R.

While various embodiments have been described above, it will beunderstood to those skilled in the art that the embodiments describedare examples only. Accordingly, the interface circuit for high speedcommunication and the system including the same described herein shouldnot be limited based on the described embodiments.

What is claimed is:
 1. An interface circuit comprising: a transmittercoupled with a plurality of wire buses, and configured to change statesof the plurality of wire buses to transmit a plurality of multilevelsymbols, wherein adjacent wire buses are electrically coupled with eachother, and the transmitter drives the adjacent wire buses to atermination voltage level.
 2. The interface circuit according to claim1, wherein the plurality of wire buses comprise first and second wirebuses, and each of the first and second wire buses comprises a pluralityof wires, and wherein the transmitter drives the first and second wirebuses to the termination voltage level by driving at least one wire ofthe first wire bus and at least one wire of the second wire bus.
 3. Theinterface circuit according to claim 2, wherein the transmitter pull-updrives the at lest one wire of the first wire bus, and pull-down drivesthe at lest one wire of the second wire bus.
 4. The interface circuitaccording to claim 1, wherein the plurality of wire buses furthercomprise a third wire bus which is adjacent to the second wire bus, andwherein the transmitter drives at least one wire of the third wire busto the termination voltage level.
 5. The interface circuit according toclaim 4, wherein the transmitter simultaneously pull-up and pull-downdrives the at least one wire of the third wire bus.
 6. A systemcomprising: a first wire bus transmitter configured to change a state ofa first wire bus based on a first multilevel symbol; and a second wirebus transmitter configured to change a state of a second wire bus basedon a second multilevel symbol, wherein, as the first wire bustransmitter pull-up drives at least one wire of the first wire bus andthe second wire bus transmitter pull-down drives at least one wire ofthe second wire bus, the first and second wire buses are driven to atermination voltage level.
 7. The system according to claim 6, whereinthe first wire bus comprises first to third wires, and wherein the firstwire bus transmitter comprises: a first output driver configured todrive the first wire to a high or low level; a second output driverconfigured to drive the second wire to a high or low level; and a thirdoutput driver configured to drive the third wire to a high or low level.8. The system according to claim 7, wherein the second wire buscomprises fourth to sixth wires, and wherein the second wire bustransmitter comprises: a fourth output driver configured to drive thefourth wire to a high or low level; a fifth output driver configured todrive the fifth wire to a high or low level; and a sixth output driverconfigured to drive the sixth wire to a high or low level.
 9. The systemaccording to claim 8, wherein two output drivers among the first tothird output drivers pull-up or pull-down drive corresponding wiresbased on the first multilevel symbol, and a remaining one output driverpull-up drives a corresponding wire, and wherein two output driversamong the fourth to sixth output drivers pull-up or pull-down drivecorresponding wires based on the second multilevel symbol, and aremaining one output driver pull-down drives a corresponding wire. 10.The system according to claim 9, wherein each of the first to sixthoutput drivers comprises a pull-up driver and a pull-down driver, andwherein the pull-up driver of the remaining one output driver among thefirst to third output drivers and the pull-down driver of the remainingone output driver among the fourth to sixth output drivers are turned onand drive the first and second wire buses to the termination voltagelevel.
 11. The system according to claim 6, further comprising: a firstwire bus receiver configured to generate the first multilevel symbolbased on a state of the first wire bus; and a second wire bus receiverconfigured to generate the second multilevel symbol based on a state ofthe second wire bus.
 12. The system according to claim 11, wherein thefirst wire bus comprises first to third wires, wherein the first wirebus receiver comprises: a first reception driver configured todifferentially amplify states of the first and second wires; a secondreception driver configured to differentially amplify states of thesecond and third wires; and a third reception driver configured todifferentially amplify states of the third and first wires, and whereinoutputs of the first to third reception drivers correspond to the firstmultilevel symbol.
 13. The system according to claim 12, wherein thesecond wire bus comprises fourth to sixth wires, wherein the second wirebus receiver comprises: a fourth reception driver configured todifferentially amplify states of the fourth and fifth wires; a fifthreception driver configured to differentially amplify states of thefifth and sixth wires; and a sixth reception driver configured todifferentially amplify states of the sixth and fourth wires, and whereinoutputs of the fourth to sixth reception drivers correspond to thesecond multilevel symbol.
 14. The system according to claim 6, whereinthe first wire bus comprises first to third wires and the second wirebus comprises fourth to sixth wires, and wherein the system furthercomprises: termination resistors respectively coupled between the firstto third wires and a common node; and termination resistors respectivelycoupled between the fourth to sixth wires and the common node.
 15. Asystem comprising: a first wire bus transmitter configured to drivestates of first to third wires to a high or low level based on a firstmultilevel symbol; and a second wire bus transmitter configured to drivestates of fourth to sixth wires to a high or low level based on a secondmultilevel symbol, wherein, as the first wire bus transmitter drives oneof the first to third wires to a high level and the second wire bustransmitter drives one of the fourth to sixth wires to a low level, thefirst to sixth wires are driven to a middle level.
 16. The systemaccording to claim 15, wherein the first wire bus transmitter comprises:a first output driver configured to drive the first wire to the high orlow level; a second output driver configured to drive the second wire tothe high or low level; and a third output driver configured to drive thethird wire to the high or low level.
 17. The system according to claim16, wherein the second wire bus transmitter comprises: a fourth outputdriver configured to drive the fourth wire to the high or low level; afifth output driver configured to drive the fifth wire to the high orlow level; and a sixth output driver configured to drive the sixth wireto the high or low level.
 18. The system according to claim 17, wherein,as at least one of the first to third output drivers drives acorresponding wire to the high level and at least one of the fourth tosixth output drivers drives a corresponding wire to the low level, thefirst to sixth wires are driven to the middle level.
 19. A systemcomprising: a first wire bus transmitter configured to change a state ofa first wire bus based on a first multilevel symbol; and a second wirebus transmitter configured to change a state of a second wire bus basedon a second multilevel symbol, wherein the first wire bus includes: afirst wire having one end coupled to a first output driver and an otherend coupled to a first common node; and a second wire having one endcoupled to a second output driver and an other end coupled to the firstcommon node, wherein the second wire bus includes: a third wire havingone end coupled to a third output driver and an other end coupled to asecond common node; and a fourth wire having one end coupled to a fourthoutput driver and an other end coupled to the second common node,wherein each of the first, second, third, and fourth drivers include,respectively, a pull-up driver and a pull-down driver configured todrive the first second third and fourth wires, respectively, to a highor low level.
 20. The system according to claim 19, wherein, when thesecond and fourth wires are driven to a middle level, only the pull-updriver of the second output driver is turned on and only the pull-downdriver of the fourth driver is turned on.
 21. The system according toclaim 19, wherein transmission termination resistors are coupled betweenfirst, second, third, and fourth output drivers and the first, second,third, and fourth wires, respectively, and wherein reception terminationresistors are respectively coupled between other ends of the first andsecond wires and the first common node, wherein reception terminationresistors are respectively coupled between other ends of the third andfourth wires and the second common node.
 22. The system according toclaim 21, wherein a resistance value of the transmission terminationresistors are changed, respectively, according to the first or secondmultilevel symbol.
 23. The system according to claim 22, wherein thetransmission termination resistors include a variable resistor.